The invention relates to a secondary braking device for a self-propelled diesel-driven roller, particularly a vibrating roller that is operated on steep downgrades only on rare occasion, and is equipped with an electronic engine control module which is programmed so as to, when a preset programmed primary diesel engine speed is exceeded, connect to ground an actuator relay on a hydraulic valve in the hydraulic system of the roller. The grounding of this actuator relay causes an interruption of the hydraulic supply pressure to one or a plurality of drum brakes, which generate maximum braking force upon the loss of the supply pressure.
In braking devices for work vehicles, such as disclosed in U.S. Pat. No. 5,983,149, the braking device is designed for frequent operation on steep downgrades, and with a varying total vehicle weight. These operating conditions have resulted in the need for a proportional braking force with an advanced control system that takes into account a number of parameters in addition to the engine speed. The system is unnecessarily complicated for a vibrating roller that is operated on steep downgrades only on rare occasion, and always at a known total weight. The primary brake system in cooperation with the internal friction of the propelling machinery and mass-moment of inertia have provided sufficient braking force in connection with the operation of prior art rollers on steep downgrades. Advancements in diesel engines have led roller manufacturers to equip their rollers with more efficient diesel engines, which are often of smaller displacement and exhibit lower internal friction. The reduction in braking force thus created results in harmful overspeeding of the propulsion machinery and exposes the roller operator to danger.
It is an object of the invention to eliminate the need for complicated prior art brake-control devices and to provide a secondary braking device that: actively engages when external circumstances tend to overspeed the propulsion machinery; uses the components of known rollers more efficiently; includes a suitable and simple control system and entails the addition of only a small number of new components.